If BioShock Remastered generated the same gross revenue on the Epic Games Store, 2K Boston, 2K Australia, Blind Squirrel, Feral Interactive (Mac) would keep approximately $24,634,926 - that's $4,241,523 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $3,222,945. Epic charges 0% on the first $1 million in annual per-app revenue and then 12% on the remaining amount. On GOG (30% cut), the developer would earn approximately $19,500,510.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.